Method and apparatus for classifying crushed material.



F. W. HUBER.

METHOD AND APPARATUS FOR CLASSIFYING CRUSHED MATERIAL.

APPLICATION FILED DEC. 23. I914. LIQGfiQQD Patented July 13, 1915.

2 SHEETS SHEET F. W. HUBER.

METHOD AND APPARATUS FOR CLASSIFYING CRUSHED MATERIAL.

APPLICATION FILED 050.23. 1914.

LMfiMQ Patented July 13, 1915.

2 SHEETS SHEET 2.

June 1 1 fo'za a. fl anon- I meaeea.

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METHOD AND APPARATUS FOR GLASSIFYING GBUSHED MATERIAL.

Specification of Letters Patent.

Application filed December 28, 1914. Serial No. 878,772;

To all whom it may concern:

Be it known that I, FREDERICK W. HUBER,

The object of the present invention is to produce a method andapparatus, by which greater efliciency can be secured in classifyingmaterials, of which we have different sizes existing in the samemlxture.

My process has been found to give excellent results in theclassification of various kinds of material, among which I mentionparticularly ground Portland cement. In the grinding of Portland cement,it is necessary to produce a product having its particles composed ofextremely fine powder, since it is only the fine material which is ableto chemically unite with the water, during the setting of the cement,the coarse material acting merely as a filler, and apparently having nomore binding power than an equal amount of sand or crushedstone wouldhave. Accordingly it isnecessary to grind or crush the cement, thenseparate the pulverulent portion from the coarse material, and returnthe coarse material to the grinder, and to repeat this process, untilall the material has been reduced to the desired degree of fineness.

Heretoforeall attempts to remove pulverulent material as formed, bymeans of air currents, have been very inefficient in that they producedan over-size product (the coarse fraction) which still contained a largeportion of the powder or flour. The

reason for this I have foundto be due'to the insuflicient length of timethat the material is left in contact with the air currents, and to theimperfect commingling of the air currents and the material, whichprevents theflour or fines from being scrubbed loose and thereby removedfrom the coarser grains. In my invention I use, to get the necessarycontact of material. and air current,

and the proper and sufficient commingling of 1 material and aircurrent,and the scrubbing or scouring action of the air current upon thematerial, a tube whose cross-section is alternately expanded andconstricted into a series of chambers and necks, whose crosssectlonalareas bear to one another a fixed relation that can be varied onlywithin very narrow limits. 7 I Anapparatus in accordance with myinvention is illustrated in the accompanying drawings, in which Y F gure1, shows (partly in section and partly 1n elevation) a completeapparatus, consisting of the classifying tube, dust separator andexhauster, and Fig. 2, shows diagrammatically the course of the currentsof air and material under treatment, in passing through the classifyingtube shown in- F1g. 1. Flg. 3 shows a portion of the connecting tube 5,and a portion of the chamber 2, on a much largerscale than the otherfigures, and the arrows therein show the currents of air or other gas,the straight arrows showing the general direction or flow of the gascurrent and the curved arrows showing the eddy currents which are set upin the maln current, when the gas passes from'the tube 5 into thechamber 2. Fig. 4

shows the modification of the apparatus in which connecting tubes areused, which connecting tubes, as shown in this figure may be ofdiflerent sizes or as shown in Fig. 2

' may be of the same size. Fig. 5 shows cham-' bers of different sizes,the chamber 6 being of large diameter relative to the pipe 7 and thetube 2 being-of small diameter, relative to the pipe 5. In thisfigure'the pipes 4, 5

and 7 are of substantially the same size, as

in Fig. 2. In 0th Figs. 4 and 5, I have shown the ratlo of the diameterof the chamber 2 to the diameter of the pipe 5 as being the smallestratio which I have found to give said results. Assuming that these areboth round .pipes the ratio of the diameters is equal to about 1.7. Inboth Figs. 4 and 5 I have shown the ratio of the diameter of the chamber6 to the diameter of the connecting pipe 7 as being about the largestratio which I have found to give good results, assuming that these pipesare round, the diameters.

being in about the ratio of 2.5 to 1.

The material to. be treated is introduced by means of the feed gate 1,into chamber 2 at a point near the-upper end of said chamher, but justbelow the air outlet 3 of said Patented July is, rare.

chamber 2, it being noted that the tube .4 projects downwardly beyondtheupper end of the tube 3, a distance not less than the diameter of thetube 4. The idea of extending this tube 4 downwardly below the tube 3 isto prevent coarse material from being blown out through tube 3, by theair or gas current. From the lower end of the chamber 2 the solidmaterial passes successively through the'neck 5, chamber 6, neck 7 tooutlet trap 8, and the material is subjected throughout all thistreatment to the action of an air blast.

By referring to Fig. 2, it Will be noted that as the air passes from theneck 7 to the chamber 6, and from the neck 5 into the chamber 2, therewill be certain eddy currents of the air set up, which will very elfec-'tively and very thoroughly scrub the material under treatment, in orderto remove from the coarse material, as much as possible of the flour orfine material, which fine material will then be carried away by the aircurrents, through the tube 3 to the dust settling chamber 9. From thepassage 3 the gases enter tangentially into the upper part of thechamber 9 and pass downwardly through the same. Theair then passesupwardly through the chamber 10. In both the chambers 9 and 10, the airmoves rather slowly, so that the greater-part of the dust settles out,and is withdrawn, continuously or intermittently through the gate 17.Introducing the air to the chamber 9 tangentially will aid the settlingout of dust, to a considerable extent. The air, together with whateverdust is still carried thereby, then passes through any suitable form ofdust filter 12 where the remaining dust is removed therefrom, and isthen led through the pipe 13 to the inlet side of the fan or pump 14..The pipe 13 is provided with a 'valve 15 by means of which the amount ofsuction at the outlet end of. the classifying tube may be regulated.

The exhauster 14 forcesinto the bottom of the pipe 7, through the outletbox 8 a-current of air with such 'a force, that the ascending air moveswith suificient velocity to readily carry material finer than a certainpredetermined grade, while the velocity is insuflicient to supportmaterial coarser than this desired grade. The suction at the point 3,exercised by the intake side of the fan 14, not only serves to removethe fines, as they are brought up by the ascending air in theclassifying tube, but this also maintains a substantially constantvelocity in the air current, and counteracts the loss of velocity headin the chambers, which naturally results from the friction between thedescending solid material and the rising air. That portion of thematerial which stays in equi librium in this regulated current of air isdisplaced downward automatically as new material is fed in, at the top,so that it is only the finest material which leaves the classifying tubethrough the pipe 3. The over-size material from the box 8 may be allowedto accumulate in the lower part of this box if desired, and its outletis perfectly regulated by means of a wing valve 16. I

The height of the scrubbing chamber is not a function of its diameter,but is dependent upon the velocity of the air current. The height of thescrubbing chamber in any case must be greater than the height to which agiven velocity of air will raise and support material of the diameter ofthat to be separated from the fines, e. 'e., the oversize. The maximumheight of the chamber will therefore be determined entirely by the rangeof grain sizes to be classified. An excess of heightover that indicatedwill, however, not detract from the efficiency of the classificationexcept that the fine material will necessarily have to be lifted thisadditional distance, and thus cause an unnecessary consumption ofenergy.

While I have shown two scrubbing chambers 2 and 6, I call attention tothe fact that any desired number of these may be employed, suitableconnections 5 being provided between the successive scrubbing chambers.The scrubbing chambers and the Cross-sectional area of scrubbing chamberCross-sectional area of connecting tube =6 is the largest ratio that canbe economically employed, while a value of 2.8 for this ratio is thesmallest that can be'used and still obtain sharp results. This ratioholds rigidly for the equivalents of tube 5 (z'. e., 4 and 7).

It will be noted that a considerable proportion of the dust likematerial will be removed from the coarse material in the first scrubbingchamber, and that the material so removed will be carried upwardly bythe air blast, and accordingly will not come again into contact with thecoarser material. It will also be noted that the coarser material fromwhich a large portion of the fine material has been removed, willthereafter be brought into intimate contact with a current of dust-freeair, in the lower scrubbing chamber, and the eddy currents in said 60the fines passing 200 mesh, the eficiency material, t e succeedingcrushing or grinding step :will bemuch more eflicient.

.While I have shown and described the may be of somewhat differentdiameters,

if desired,-and likewise the scrubbing chambers 2 and 6 may also be of.difierent diameters if so desired. The chambers also may besubstantially cylindrical (or rectangular, having uniform cross sectionthroughout their height) or if so desired they maybe. of other shapes. gI v The classifying column is illustrated as vertical in theannexeddrawing, and'while I prefer to have this vertical, I callattention to the fact that it may be inclined without departing from thespirit of myinvenf tion.

' While I have described air as the fluid to be employed in carrying outmy process, I call attention to. the fact that other gases may be used.The gas to be usedwill obviously be one that-will not injuriously affectthe particular material being clas- While I have described the inventionas applied particularly to the manufacture of Portland cement, it.will'be noted that various other materials composed 'of coarse and fineparticles of substantially the same specific gravity .may betreated, andI do not restrict the application of the novelprinciples hereindisclosed, to the treatment of cement.

While the proportions may vary more or less, as above stated, I give thefollowing example, which istlffor illustration only and not for thepurpode of limiting the invention. In' this invention Portland cement isthe material treated.

In the classification; of Portland cement, the tubes 3, :t, 5 and [mayhave'an internal diameter of 4% inches and the scrubbing chambers aninternal diameter of 10 inches, the ratio of cross sectional area of thescrubbing chamber tothat of the tube in this example being 100:20i orabout 5:1. The combined height of the parts 457 and of the parts 26 maybe 18 and l8 inches respectively. With these dimensions, the pressure ofthe air entering the box 8 will preferably be about lb. per square inch,and the suction to be appliedthrough the tube 3 will preferably be equalto lb. per

square inch, below atmospheric. In this example, the material treatedfor classificatlon being ball-mill product ranging from 3; 1IlCllmaterial down to dust, and practically all of process, for an entiredays run, has been as high as 98%.

It will be noted that in my method of l classification, the entire aircurrent enters License tubes 4, 5 and 7 as being of the-same diameter, Icall attention to the fact that these the lower end ofthe classifyingcolumn, and passes out at the upper end of the column, and that all thedust separated from the material passes out through the outlet 3.

What I claim is v a 1. A process of classifying a materialwhich'comprises feeding a stream of a material consisting essentially ofa mixture of coarse and fine particles of substantiallythe same specificgravity, into an ascending current of'gas, at a level locatedashort'distance below the upper end ofsaid gas current, introducing all of thegas comprising said gas current at'the lower end thereof,

and withdrawing all said gas at the upper at end of said gas current,maintaining the force 'of the. said gas current at all points in theheight thereof, sufiiciently great to support the fine but not thecoarse particles contained .in said mixture to be classified, causingsaid gas current to repeatedly material to be classified, and producingeddy currents in said gas current, at a plurality of points in itsheight, and thereby subjecting the material to a scrubbing action untilthe pure material. is detached from the coarse and carried therefrom.

2. A process of classifying a material which comprises feeding a streamof a mate rial consisting essentially of a mixture of coarse and fineparticles of substantially the same specific gravity, into an ascending.cur- .rent of .gas, at a level located a short dis tance below the'upper end of said gas current, introducing all of the gas comprisingsaid gas current at the lower end thereof points in'its height,supplying the gas to the bottom of theclassifying column, sucking offthe gas and suspended fine material carried thereby from the upperportion of the classifying column at a point somewhat above that atwhich material to be classified enters said column, and removing thedust from said gas.

3. A classifier comprising an upwardly extending series of verticallyelongated scrubbing chambers and connecting pipes of less diameter thansaid scrubbing chambers, a gas outlet near the top of the uppermostscrubbing chamber, a feed inlet located at a point somewhat below saidgas outlet, and means for passing a current of gas upwardl through saidchambers and pipes.

4. n a classifier, the combination of an alter its velocity while incontact with the upwardly extending classifying column elongatedscrubbing composed of alternately arranged vertically chambers andconnecting pipes of less diameter than said scrubbing chambers, dustseparating means connected to the upper part of said column, and meansfor withdrawing the dust-laden gas from the column at ,a point located ashort distance above the inlet for solid material, through saidseparating means.-

5. In a classifier, a classifying column composed of alternatelyarranged vertically elongated scrubbing chambers and connecttroducingmaterial to be classified to said column and means for passing a currentof gas through said column.

In testimony whereof I aflix my signature in presence of two witnesses.

FREDERICK W. HUBER. Witnesses:

NORMAN MACBETH, J. D. MEYER.

